What is a triathlon bike split calculator?

It estimates the bike leg from distance, FTP, target intensity factor, course profile, and setup, then reports target watts, speed, split, and TSS.

What intensity factor should I use for Ironman?

Many age-group athletes plan roughly 0.68-0.73 IF for full-distance racing, then adjust for heat, hills, and run durability.

What intensity factor should I use for 70.3?

Many 70.3 plans sit around 0.75-0.82 IF, but the right value depends on fitness, course difficulty, and how well you can run afterward.

Is this a physics simulator?

No. It is a practical estimate using broad modifiers. For course-specific optimization, use a dedicated course-file model.

Power-based bike pacing

Triathlon Bike Split Calculator

Estimate a realistic race bike split from FTP, intensity factor, W/kg, course profile, and setup before you commit to the whole race plan.

Race distance

Bike distance

FTP

Body mass

Intensity factor

Course profile

Bike setup

Controlled 70.3 effort

02:56:28

Projected bike split

Watts

187 W

Speed

30.6 km/h

W/kg

2.49

TSS

179

Bike split checks

Speed is estimated from broad modifiers, not a course-file physics simulation.

Connect this to the race plan

Full race plannerBuild a complete Ironman or 70.3 plan from pace to nutrition.Run off the bikeCheck whether this bike effort protects your run split.Cutoff bufferSee whether the bike split leaves enough course-closure buffer.Fueling planTurn bike duration into bottles, gels, carbs, and sodium targets.

How to use the result

Start with a recent FTP, choose a race distance, and keep intensity factor conservative enough that the run still exists. The calculator turns the power target into watts, W/kg, estimated speed, split time, and bike TSS.

Use lower IF for Ironman than 70.3 or Olympic racing.
Treat hilly, windy, or technical courses as run-risk multipliers.
Use TSS as a warning, not a medal for riding hard.

Example race read

A 220 W FTP athlete riding a 70.3 at 0.78 IF targets about 172 W. If the course is rolling and the setup is average, the projected split should be checked against the run-off-bike calculator before calling the plan aggressive or realistic.

Common mistakes

The most expensive mistake is chasing a bike split in isolation. A fast ride that creates high TSS, missed fueling, or a heavy first 5 km of the run is not a good triathlon split. The right bike target protects total finish time.

Next best calculators

Run Off The BikeEstimate the run cost of the bike target before race day.Course AdjustmentApply terrain and course friction to the split estimate.Goal Split PlannerConnect bike watts back into the full swim-bike-run target.

Trust and methodology

How this page should be used

Last updated

July 13, 2026

Maintained by

M Imtinan Farooq

Status

Planning estimate, not a race guarantee

Formula summary

Target watts = FTP x IF; TSS = hours x IF squared x 100; speed uses broad modifiers.

Key assumptions

FTP, body mass, course profile, and setup are realistic for the race.

Limitations

Not a GPS course-file physics model and not a CdA/Crr/wind simulation.

Full formulas, source notes, and limitation details are maintained on the methodology page. Use official race guides for event rules, cutoff times, venue policies, and safety instructions.